The invention relates to an endoscope comprising an endoscope tube and a lens system with several lens components and air gaps arranged between the lens components as well as a light source, all parts being arranged within the endoscope tube. At least individual lens components have different axial lens lengths relative to one another and the shortest lens components are arranged in the area of the axial center of the endoscope tube.
Such an endoscope is disclosed in German patent document 203 06 541 U1. The endoscope can be bent greatly without damaging it because the shorter lens components are arranged in the area of the axial center of the endoscope tube. However, the bending characteristics of the endoscope are to be improved further.
Another endoscope is disclosed in German patent document 199 42 152. In this endoscope, between the objective and the ocular an optical image transmission system comprising several achromatic lenses is arranged. All lenses are identical. Disadvantageously, the endoscope tube can be bent only insufficiently during use in an operation or surgery.
U.S. Pat. No. 2,828,669 also discloses an endoscope wherein between the ocular and the objective doublets are arranged. All eight doublets are identical and the spacings between the individual doublets are also almost identical.
German patent 33 42 498 discloses an endoscope which is comprised of a plurality of lens assemblies wherein the lens assemblies are comprised of two lens members. The individual lens members have different lengths. Between the individual lens members there are no air gaps but between the lens members a glass plate is arranged so that flexing of the endoscope tube is prevented.
In another known endoscope, the lens system is comprised of several rod lenses having essentially identical length. When using the endoscope during an operation or surgery, for example, in the knee area, or for a urinary tract examination, bending of the endoscope tube occurs frequently. In the known endoscope, the endoscope tube can be deflected at its distal end (end distal to the operator) by approximately 20 mm. When bending is greater than this range, this disadvantageously leads to damage of the endoscope, in particular, breakage of the rod lenses can result.
Moreover, endoscopes are known in which the lens system has several sequentially arranged triplet systems. A triplet system is comprised of a long rod lens, a short lens, and another long rod lens.